I'm looking very hard at the 2020 GMC 2500HD Gas. Will be a 6.6L with 401 hp and 460 ft/lb. And a payload of just under 4000 lbs. But not available until June (ish) and I won't be looking until next year anyway. I tow now with a 2015 Sierra 1500 max trailer, 5.3L.
If I were to go diesel, I would pass by the 2500 and go 3500. It's not so bad with the 2020's, but 2019 and older you'll find you don't have much more payload with a 2500 diesel vs. what you have now. I'm at 2015 for payload and most of the 2500 diesels I've seen are much more than 2300 lbs. I'm comparing CC numbers.
I don't tow as much as you are (8,200 lbs wet) and my truck is good enough for now.
I've had a diesel in the past (01 2500 Duramax) and also had a short commute (~3.5km) and would end up parking the diesel in the winter and by a POS for a few months as the diesel never got to operating temps. I'm not looking to get back into a diesel anytime soon for that reason. I just don't work it hard enough 90% of the time.
Outside of power, the biggest difference in the gas vs diesel will be the tranny. Again, I'm only talking the GMC here, but the diesel has a 10 speed version of the Allison (not actually made by Allison anymore) and the gas will be a 6 speed. And you will get more engine braking with a diesel.
The 6.6 gas will not have the power of your 6.2L. That is a nice motor. But it will be better than the current 6.0L in the HD trucks.
